Starting on Saturday, March 13th, 2021, the Let's Have Fun! Spring, Pokécard (楽しもう。春、ポケカ。) campaign to give away a sticker and promo cards will be held at Pokémon Card Gyms nationwide in Japan. The number of promo items is limited. If you purchase at least one box or 30 packs at a store, you will receive a set of four promo cards including: Potdeath, Galarian Mr. Rime, Dedenne and Horubee.


Source: https://www.pokemon-card.com/info/2021/20210305_002815.html